Repeated mechanical or electrical operations, such as cleaning, transfer, or image development processes; or, electrical charging processes, such as roller electrical charging and corona electrical charging; affect the surface of photosensitive bodies. Because the surfaces of photosensitive bodies are subjected to wear and undergo degradation due to friction and such during cleaning or electrical charging, there is a demand for improvements in durability of photosensitive bodies.
Attempts to improve characteristics by reducing surface energy by adding polydimethylsiloxane oil, polytetrafluoroethylene, and the like, to the photosensitive layer itself are known in the art.
Furthermore, attempts have been made to form a new protective layer on the surface of the photosensitive body. For example, using coating materials obtained by dispersing electrically conductive particles in various resins was suggested in JP-A-57-30843 (1982). Applying to photosensitive body surfaces, a surface-protecting layer of crosslinked polysiloxane composed of a product of joint hydrolytic condensation of a trifunctional alkoxysilane and a tetrafunctional alkoxysilane was suggested in JP-C-05-46940 (1993).
Because the solubility of fluorine-containing high polymers, such as polytetrafluoroethylene, is extremely poor and an optically uniform dispersion is extremely difficult to obtain, and because the computability of fluorine-containing high polymers is poor when they are added to resin, agglutination and optical scattering occur. Additionally, such high polymer particles can bleed onto the surface of the photosensitive body. When polysiloxanes are added, the tendency to bleed is quite strong, and the effects are not long lasting.
When resins containing metal oxide particles were used in the protective layer, surface hardness improved. However, surface energy increased, cleaning characteristics became inferior, and particles underwent agglutination, producing optical scattering. Also, forming the protective layer of polysiloxane was detrimental to the charge transfer properties of the photosensitive body due to the insulating properties of the polysiloxane.
One object of this invention is to provide a process for the preparation of a coating material that forms a protective layer for electrophotographic photosensitive bodies. A further object of this invention is to provide a coating material that is not detrimental to the functionality required of the electrophotographic photosensitive bodies and that has superior optical uniformity, low surface energy, and superior surface hardness.